python - 在 Python 中过滤字符串

Question

我正在制定检查字符串(电子邮件)的算法——比如“电子邮件地址有效”，但它们是规则。电子邮件的第一部分必须是包含 1-8 个字符的字符串(可以包含字母、数字、下划线 [_]...电子邮件包含的所有部分)，@ 之后电子邮件的第二部分有具有 1-12 个字符的字符串(也包含所有合法表达式)并且必须以顶级域 .com 结尾

email = raw_input ("Enter the e-mail address:")
length = len (email)
if length > 20 
    print "Address is too long"
elif lenght < 7:
    print "Address is too short"  
if not email.endswith (".com"):   
    print "Address doesn't contain correct domain ending"   
try:
    first_part = len (splitting[0])
    second_part = len(splitting[1])  

    account = splitting[0]
    domain = splitting[1] 

    list = "abcdefghijklmopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_."

    for c in account: 
        if c not in list:
            print "Invalid char", "->", c,"<-", "in account name of e-mail"

    for c in domain:
        if c not in list:
            print "Invalid char", "->", c,"<-", "in domain name of  e-mail"

    if first_part == 0:
        print "You need at least 1 character before the @"
    elif first_part> 8:
        print "The first part is too long"
    if second_part == 4:
        print "You need at least 1 character after the @"
    elif second_part> 16:
        print "The second part is too long"
except IndexError:
        print ""The address must consist of 2 parts connected with symbol @,\
 and ending must be .com"

    if first_part > 0 and first_part < 8 and second_part >4 and second_part < 16:
       print "Valid e-mail address"

Answer 1

Regular expressions好吧!

import re

address = 'test@gmail.com'
if re.match(r'^[a-z0-9_]{1,8}@[a-z0-9_]{1,8}\.com$', address, re.IGNORECASE):
  print 'valid'
else:
  print 'invalid'

一个较短的正则表达式(如注释所示)是 r'^\w{1,8}@\w{1,8}\.com$'

我不知道那是不是你老师的目标，但知道正则表达式总是好的:)